Heating tube



Patented Aug. 16, 1932 PATENT OFFICE RICHARD THUBM, OF SAGINAW, MICHIGAN HEATING TUBE No Drawing.

This invention relates to improvements in the Well-known method of heating by heating tubes, commonly called Perkins tubes, according to which baking chambersa-nd the 5 like enclosed in the Walls of an oven are heated by means of hermetically closed tubes containing a liquid suitable for the transference of heat, usually water, and extending with their longer portion, the heat-transferring part, within the baking chamber and passing then through the Wall surrounding the latter, with its comparatively short end into the fire gases of the furnace, where they absorb the heat required.

Water, which, as mentioned above, is hitherto generally employed as filling of Perkins tubes, has great heat-transferring power, but its low boiling point and critical temperature prevent it from being used effectively 0 and without danger of too high pressure within the tubes, Where temperatures above 315 C.=600 F. are required in the baking chamber or the like to be heated.

The object of my invention is to provide such a filling for the Perkins tubes, that they can be safely and efliciently employed to heat baking chambers and the like to very much higher temperatures than those named above. To this end, my invention consists therein that I charge the Perkins tubes with a liquid alloy of alkali metals with each other, preferably of potassium and sodium. The alloy which I preferably employ consists of 50-75% potassium and 50-25% sodium, which is liquid at ordinary temperature. Its melting point ranges according to its composition from -10 O. to +6 C.=14-42.8 F. and its boiling point from 7 20800 C.=1328- 1472 F.

It will be understood that, when using alloys of alkali metals as filling, the tubes must be absolutely dry and in their interior as free as possible of any oxides, and that, after they receive their due charge of the alloy, they r are closed immediately. I evacuate the tubes before charging and fill and close them hermetically under vacuum.

I claim:

1. The method of making heating tubes of the type described, which consists therein,

charged with the required quantity Application filed October 28, 1929. Serial No. 403,122.

that the tube to be used is first evacuated, tiien o a liquid alloy of alkali metals with each other, serving as heat-transferring medium, and thereafter hermetically closed under vacuum. 2. The method of making heating tubes of the type described, which consists therein, that the tube to be used is first evacuated, then charged with the required quantity of an alloy, composed of 50-75% potassium metal and 50-25% sodium metal, serving as heat-transferring medium, and thereafter hermetically closed under vacuum.

RICHARD THUBM. 

